1. Field of the Invention
The present invention relates to a vehicle travel safety device which, in the case where a driver actively carries out a braking operation when it is determined that there is a possibility of the subject vehicle coming into contact with an object, generates a braking force to support the braking operation by the driver.
2. Description of the Prior Art
In the prior art, the distance between the subject vehicle and a vehicle in front is detected by an ultrasonic sensor or an infrared sensor. Automatic braking is carried out when the above-mentioned distance between the vehicles becomes less than a threshold value where there is a possibility that the subject vehicle might come into contact with the vehicle in front. Japanese Utility Model Registration Publication No. 2573248 has proposed that, when an occupant does not wear a seat belt, the deceleration rate of the automatic braking is set at a small value so as to prevent the occupant from moving forwards due to the inertia accompanying the braking.
Furthermore, when considering the difficulty of effectively exhibiting the performance of an air bag in restraining an occupant when proximate expansion of the air bag (expansion of the air bag in a state in which its distance from the occupant is too small) is effected during collision of a vehicle, Japanese Patent Application Laid-Open No. 3-159838 has proposed that the distance between the air bag and the occupant is detected on the basis of the position of the seat on the lengthways slide, the angle of inclination of the seat back, the length of the seat belt that is extended, etc. and the timing of the expansion of the air bag is changed according to the distance.
However, with regard to the above-mentioned Japanese Utility Model Registration Publication No. 2573248, since the problem of proximate expansion of the air bag at a time when automatic braking is operated is not considered, there is a possibility that the performance of the air bag might not be exhibited effectively. Furthermore, with regard to the above-mentioned Japanese Patent Application Laid-Open No. 3-159838, since the distance between the air bag and the occupant is detected in a non-decelerating period, forward movement of the body of the occupant due to the deceleration resulting from automatic braking is not considered and there is a possibility that proximate expansion of the air bag might result.